In the construction of buildings, a pit is usually excavated into which the footings and underground portions of the building will be erected. It is common for excavations to go down three or four floors at least. The sides of the pit are usually substantially vertical, and in order to support the earth around the pit, I-beams or piles, are installed at intervals. These beams or piles are driven in by pile drivers, down into the earth prior to or during excavation, as well known in construction practice. Side Wall panels, such as concrete or the like, are then formed or placed between the vertical I-Beams as excavation continues downwardly. In this way the sides of the pit are maintained and supported, without collapsing into the pit. It is however, not an unusual experience for the concrete or side wall panel material or earth around the upper edge of the pit at or close to ground level, will start to deteriorate and portions of debris may fall down into the pit. This is both hazardous, and also constitutes material which must eventually be removed for the construction of the underground portion of the building to proceed uninterrupted.
In addition to this, while the pit is being excavated, and even after the underground portion of the building has been erected, the edge of the pit remains a hazard to workers and pedestrians alike. It has been the practice for years to install safety barriers around the grade level edge of such a pit, in order to prevent any accidents occurring to workers and pedestrians around the edge of the pit.
In addition to this, it is now becoming desirable to install some protective barrier extending from the grade level edge of the pit downwardly, so as to then prevent debris falling from the upper portions of the wall panel materials holding the earth in place.
The erection of such barriers, both below grade level and above grade level is becoming an essential feature of modern day construction. Numerous forms of safety barriers have been proposed in the past, which can be erected around an open pit at grade level. However, these prior proposals are not generally suitable for erection around major excavations such are the practice in the erection of high rise buildings. In these cases, excavation will start and the piles will be driven into the earth around the perimeter of the excavation. Once excavation has removed more than a small portion of the earth, it becomes difficult to erect a safety barrier around the perimeter. The safety barrier should be securely erected so as to retain the earth and wall panels around the upper edge of the pit or excavation. In addition, the safety barrier preferably will extend above the perimeter of the pit, ie. above grade level, for personal safety. Securing such a safety barrier in position around a large excavation is a difficult and challenging problem. In addition, since the construction of the barrier will involve a substantial cost and material resources, it is desirable, as far as possible, that it is capable of being removed when the building is completed, or at a stage where the site is no longer hazardous, and the barrier can then be reinstalled around a new building site.